Dew Straps - Power Question

[Spaced Out]

Hi All

Just got my first refractor and need to sort out some dew straps for this and a guidescope. I have a pier with mains sockets, so just wondering if I can I run 2x dew straps (via a splitter) straight from a 12v switching power supply plugged into a mains socket ?

Thanks

Edited July 25, 2022 by Spaced Out

[fifeskies]

While that will work it gives no control over the heating straps , ie full on all the time.

You generally need to reduce from full output, mine run around 20% to 40%.

Only higher if very heavy dew on a cold night.

There are several options for in-line control that sit between the PSU and the heating strap itself.

[Gabby76]

You should not power dew straps directly, they need a controller so that you can regulate the heating required.

You only want to keep the equipment a degree or two above the dew point. 

I use either a older Kendrick Mk IV 2 channel controller or a Thousand Oaks 4 channel controller. 

[Spaced Out]

Thanks both for the replies. I was just looking to keep it as simple (and cheap !) as possible, so, I guess I should have asked is a dew controller essential for running dew straps ? Sounds like it is.

[Pixies]

Dew Control are a UK company that produce low power straps that don't require a controller:

https://www.dewcontrol.com/Dew_Heater_Straps_-_All_Sizes/p3099125_14674363.aspx

 

[Gabby76]

The Dew Control straps do require a controller as well, without one the strap will continue to increase in temperature. 

From your link: Compatible with all popular controllers, but work especially well with our own.

[Pixies]

3 hours ago, Gabby76 said:

The Dew Control straps do require a controller as well, without one the strap will continue to increase in temperature. 

From your link: Compatible with all popular controllers, but work especially well with our own.

Doh! Sorry - wrong site!

https://dewheater.com/?page_id=2

 

[Carbon Brush]

Don't forget your power supply has to be sized as if ALL dew straps are on ALL the time.
Controllers turn the power on/off at intervals. At some point they may all be on.
Depending on the type of power supply, it may just reduce voltage a bit, or it may shut down.
With a battery, you don't have this problem. You could consider a powertank/bank/whatever trickle charged?

You should of course use separate supplies for mount & dew.
The last thing you want is a confused 🥴mount because the deew straps have pulled the 12V supply down to 8V.

HTH, David.

[Spaced Out]

50 minutes ago, Pixies said:

Doh! Sorry - wrong site!

https://dewheater.com/?page_id=2

 

Thank you, they look interesting. Could be the simple solution I am looking for. 👍

[Spaced Out]

36 minutes ago, Carbon Brush said:

You should of course use separate supplies for mount & dew.
The last thing you want is a confused 🥴mount because the deew straps have pulled the 12V supply down to 8V.

HTH, David.

Good advice ! Thanks.

[Zeta Reticulan]

Not sure how relevant this is, but a multichannel controller is always useful. Especially if you want to heat the finder as well.

Another thing I've discovered about refractors over the years is that you can never have a long enough dew shield. I usually add a flexible dew shield to the existing dew shield. I find that this usually means I don't need a heated strap at all most nights. 

[Gabby76]

9 hours ago, Pixies said:

Doh! Sorry - wrong site!

https://dewheater.com/?page_id=2

 

Unfortunately they are quite low power straps so they may not be able to keep up with high humidity.

I also could not find any posting of what the actual output in amps/ milliamps are. 

[Len1257]

3 hours ago, Gabby76 said:

I also could not find any posting of what the actual output in amps/ milliamps are. 

In the description for each strap they quote the voltage and wattage. ie 12V and 3W, so 0.25A or 250mA.

Quote

W&W Astro dew heater 15 cm strap is designed to fit 2” eyepiece or finderscope. Works with 12V power supply and produces 3W of power.

Of course this varies for each size.

[Gabby76]

They do look interesting but I wonder how well they would work in colder temperatures/ high humidity without being able to increase/ decrease the power.

One of my local viewing areas is beside a bog so humidity can be a issue some nights.